Re: support for sata7 Streaming Feature Set?

From: Mark Lord
Date: Thu May 18 2006 - 09:25:25 EST

Tejun Heo wrote:
Jan Wagner wrote:
Hi and thanks for your response,

On Sun, 14 May 2006, Tejun Heo wrote:
anyone know if the now already somewhat old Streaming Feature Set of
ATA/ATAPI 7 is going to be implemented in the kernel ata functions?

According to one web site that contains hdreg.h
That link just gives me a search page. Got a better link?

No, it's not a horrible hack. Again, no one thinks smartd is a horrible hack. Even core things like irqbalancing and CPU speeding down are controlled from userland. Being in the userland is a good thing - it's much safer & more convenient/flexible out there.

What are you gonna use it for?

To record or play back real-time continuous streamed data that is not
error-critical but delay critical, from/to a bidirectional data
aquisition card at ~1Gbit/s over longer time spans.
Other uses include tons of embedded systems using Linux,
primarily those that handle any kind of A/V record/playback
(think "Tivo", MP3 player, video players, ...).
These are about as rare as a fileserver, when counting the installed base.

I think that the ATA streaming feature set cannot be done
efficiently (which is the whole point of it!) without some kernel support.

The device driver has to know about it, at a minimum so that it can
select a different EH protocol for the streams. Which in turn means
that the streaming commands should be known to the driver as well.

But how to handle it all nicely is the real question.
A new block driver, if libata cannot handle it?

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